// Copyright 2014 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef CONTENT_BROWSER_DEVICE_SENSORS_DEVICE_SENSOR_SERVICE_H_
#define CONTENT_BROWSER_DEVICE_SENSORS_DEVICE_SENSOR_SERVICE_H_

#include <memory>

#include "base/callback_forward.h"
#include "base/macros.h"
#include "base/memory/shared_memory.h"
#include "base/memory/singleton.h"
#include "base/threading/thread_checker.h"
#include "content/browser/device_sensors/device_sensors_consts.h"
#include "content/common/content_export.h"
#include "mojo/public/cpp/system/buffer.h"

namespace content {

class DataFetcherSharedMemory;

// Owns the data fetcher for Device Motion and Orientation and keeps track of
// the number of consumers currently using the data. The data fetcher is stopped
// when there are no consumers.
class CONTENT_EXPORT DeviceSensorService {
public:
    // Returns the DeviceSensorService singleton.
    static DeviceSensorService* GetInstance();

    // Increments the number of users of the provider. The Provider is running
    // when there's > 0 users, and is paused when the count drops to 0.
    // Must be called on the I/O thread.
    void AddConsumer(ConsumerType consumer_type);

    // Removes a consumer. Should be matched with an AddConsumer call.
    // Must be called on the I/O thread.
    void RemoveConsumer(ConsumerType cosumer_type);

    // Returns the shared memory handle of the device motion data.
    mojo::ScopedSharedBufferHandle GetSharedMemoryHandle(
        ConsumerType consumer_type);

    // Stop/join with the background polling thread in |provider_|.
    void Shutdown();

    // Injects a custom data fetcher for testing purposes. This class takes
    // ownership of the injected object.
    void SetDataFetcherForTesting(DataFetcherSharedMemory* test_data_fetcher);

private:
    friend struct base::DefaultSingletonTraits<DeviceSensorService>;

    DeviceSensorService();
    virtual ~DeviceSensorService();

    bool ChangeNumberConsumers(ConsumerType consumer_type, int delta);
    int GetNumberConsumers(ConsumerType consumer_type) const;

    int num_light_readers_;
    int num_motion_readers_;
    int num_orientation_readers_;
    int num_orientation_absolute_readers_;
    bool is_shutdown_;
    std::unique_ptr<DataFetcherSharedMemory> data_fetcher_;
    base::ThreadChecker thread_checker_;

    DISALLOW_COPY_AND_ASSIGN(DeviceSensorService);
};

} // namespace content

#endif // CONTENT_BROWSER_DEVICE_SENSORS_DEVICE_SENSOR_SERVICE_H_
